Sugarbaker Oncology Associates
Specialty Section for the Treatment of Appendix Cancer
and the Pseudomyxoma Peritonei Syndrome

Pseudomyxoma Peritonei Syndrome Defined

The term pseudomyxoma peritonei is literally interpreted as "false mucinous tumor of the peritoneum". It is most commonly applied to a slowly progressive disease process characterized by extensive mucus accumulation within the abdomen and pelvis. Such a broad definition allows both mucinous adenomas of the appendix and mucus-producing gastrointestinal adenocarcinomas to be included together under this term.

On the basis of the results of recent studies, we have proposed that the term pseudomyxoma peritonei syndrome be strictly applied to a pathologically and prognostically homogeneous group of cases. These cases are characterized by histologically benign peritoneal tumors that are frequently associated with an appendiceal mucinous adenoma and have a unique natural history. Pathologically, the peritoneal mucinous lesions are termed "disseminated peritoneal adenomucinosis" or simply "adenomucinosis". Cases of peritoneal carcinomatosis, regardless of the presence of abundant extracellular mucin, are excluded from this definition. Clinically, the term pseudomyxoma peritonei describes a syndrome that produces its symptoms by copious mucus tumor production which results in a "jelly belly". Although this tumor is not considered biologically aggressive because it does not metastasize via the lymphatics or blood stream like gastrointestinal adenocarcinomas, it is a deadly process. The space required within the abdomen and pelvis for nutritional function eventually becomes replaced by mucinous tumor. Pseudomyxoma peritonei always results in the death of the patient unless definitively treated.

Redistribution of Peritoneal Adenomucinosis

Virtually every known solid tumor has the primary malignancy near the epicenter of the cancerous mass. With few exceptions, at the time of diagnosis, the primary tumor is the most massive tumor deposit and causes the symptoms that bring the patient to the physician. In contrast, with pseudomyxoma peritonei, the primary tumor is usually inconspicuous and rarely causes symptoms because of its size. The current thinking regarding the pathophysiology of pseudomyxoma peritonei can be summarized as follows. An adenoma arises within the appendix, and with progressive growth, the small interior cavity of the appendix becomes occluded. This occlusion of the lumen leads to distention of the appendix, not only by mucus produced by the normal appendiceal tissue but by the mucinous tumor. The appendix eventually ruptures, first causing a "blowout" and then a slow leak of mucus containing epithelial cells from the adenoma. After the appendix decompresses, the perforation may reseal, only to extrude more adenomatous epithelial cells at a later time.

Tumor cells that escapes into the free peritoneal cavity do not implant and grow in the immediate vicinity of the appendix. Rather, most of these tumor cells are surrounded by a slippery fluid and move in the normal flow of peritoneal fluid. Unlike carcinoma cells that implant in a random fashion near the point of bowel perforation, peritoneal adenomucinosis cells accumulate at specific abdominal and pelvic sites and are excluded from accumulation at other locations. The most important factor that determines the localization of adenomucinosis cells is the absorption of peritoneal fluid. Bulky deposits are often found within the greater omentum, lesser omentum and beneath the right hemidiaphragm. Gravity provides a second mechanism whereby adenomucinosis cells are distributed in the peritoneal cavity. Dependent portions of the abdomen and pelvis, such as the cul-de-sac of Douglas, the right retrohepatic space, the left abdominal gutter, and the fossa created by the ligament of Treitz, become filled with a mucoid tumor mass.

Perhaps the most consistent observation during surgical exploration of patients with pseudomyxoma peritonei syndrome is the complete or nearly complete absence of mucinous tumor on the intestinal surfaces. The exceptions to this are the antrum of the stomach and pylorus, the ileocecal valve region, and the rectosigmoid colon within the pelvis. All three of these sites are fixed to the retroperitoneum and are not free to move as a result of peristaltic activity. Apparently, the nearly continuous peristaltic activity of the small bowel prevents mucinous tumor implantation on the small intestine and its mesentery.

Symptoms and Signs

For both males and females, the most common presenting symptom is a gradually increasing abdominal girth. In males, the second most common symptom is an inguinal hernia. In women, the second most common symptom is an ovarian mass palpated at the time of a routine pelvic examination.  Some patients thought to have appendicitis will later be found to have an appendiceal mucinous tumor. Some of the earliest diagnoses are in women in whom the disease was detected at laparoscopy performed for infertility. A laparoscopic diagnosis of mucinous appendiceal tumor is becoming increasing frequent.

Cytoreductive Surgery and Perioperative Chemotherapy

Because the adenomucinosis associated with pseudomyxoma peritonei syndrome is minimally invasive and yet extensively coats parietal surfaces, a series of peritonectomy procedures were developed. These involve stripping the parietal peritoneum and resecting structures at fixed sites that contain adenomucinosis. Please see our
Manual for Physician and Nurses for a more detailed description of cytoreductive surgery.

Direct administration of selected chemotherapy agents into the peritoneal cavity permits delivery of high concentrations of drug directly to abdominal and pelvic surfaces where the tumor is located. This pharmacologic advantage is the result of the peritoneum-plasma barrier. A major problem in the past with intraperitoneal chemotherapy delivery involved nonuniform drug distribution. This resulted from intestinal adhesions, from tissues closed off by sutures, and from pooling of intraperitoneal fluid at dependent sites. The use of
Heated Intraoperative Intraperitoneal Chemotherapy (HIIC) after complete dissection of an adhesive process and before anastomoses are completed, minimizes this problem. HIIC not only improves drug distribution, but improves the drug penetration into tissue compared to normothermic drug administration.

Our clinical pathway for the treatment of pseudomyxoma peritonei syndrome is presented below.

HIIC = Heated intraoperative intraperitoneal chemotherapy; EPIC = Early postoperative intraperitoneal chemotherapy; IV = Intravenous chemotherapy;                                 IP = Intraperitoneal chemotherapy; MMC = Mitomycin C; DOX = Doxorubicin; 5-FU = 5-fluorouracil; CT = Computed Tomography

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